In keeping with MARCE-2 goals of developing broadly applicable novel therapeutics, models, and approaches to improving innate and acquired host defenses for important health threats, this project builds upon substantial progress and several publications on developing new models and quantifying both clinical outcomes and intensity and duration of infection with the highly chlorine resistant water borne Cryptosporidium spp. In particular, our neonatal mouse model mimics the effects of cryptosporidial infections in humans causing both growth shortfalls and greatly increased infection severity in the presence of malnutrition. We now have very promising pilot data suggesting that key mucosal repair agents, including alanylglutamine and arginine as well as selected candidate vaccines (from VCU and UMD collaborations), given intranasally elicit immune responses that reduce both intensity and growth impairment from cryptosporidial infections. Thus, our broad, long term objective is to define the optimal mucosal repair agents and their potentially synergistic interactions with documented drivers of innate and acquired immunity to either prevent or ameliorate cryptosporidial infections and their clinical consequences. Our specific aims will therefore be: 1) to define the effectiveness of alanylglutamine, arginine, and APOE mimetic peptide, given before or after cryptosporidial infection, 2) to determine the interactions and potential synergies of these mucosal repair agents given with CpG, IMO or ClyA-pSEC vaccine vector drivers of innate immunity or with ClyA-CVD908htr-CP15 driving adaptive immune responses; and finally 3) to compare the relative efficacies and potential synergies of the optimal regimen defined above with the marginally effective, but best available anti-protozoal drug nitazoxanide in both our organoid and neonatal mouse models challenged with Cryptosporidium parasites. This approach not only will identify optimal mucosal and immune enhancing approaches to cryptosporidial infection, but will have potential relevance to other enteric infections and vaccines as well.